Effective isolation protocol for secondary metabolites from saffron: semi-preparative scale preparation of crocin-1 and trans-crocetin

Abstract

Extracts from saffron, the dried stigmata from Crocus sativus L. are recognized as valuable tools for pharmaceutical development in neuroprotection and antidepressive therapy. One major lead compound is crocin-1 (1), which gets metabolized to the C20-dicarboxylic acid trans-crocetin (2) being responsible for potential NMDA-antagonistic effects in the central nervous system. Neither crocin-1 nor crocetin are commercially available in sufficient quality and to a reasonable price. The following protocol describes effective methods to obtain both compounds from an EtOH-water extract (2:8) in good yields (about 43% related to the starting material). Crocin-1 (purity>90%) can be obtained from the extract by means of partition chromatography (FCPC) in a single run without fractionation of the mobile phase by using only the stationary phase and in yields of about 48%, related to the saffron extract. Trans-crocetin can be obtained from the EtOH-water extract by enzymatic deglycosylation of crocins using commercially available cheap glycosidase mixtures as e.g. Röhm Enzyme® or RohamentCL®. Further polishing can be achieved by flash chromatography on MCI® stationary phase with yields between 6 and 11%. The protocols described provide effective isolation of crocin-1 and trans-crocetin reference compounds for further preclinical and analytical studies with saffron extracts.

Keywords: Crocetin; Crocin; Crocus sativus L; Isolation.